Piezoelectric element

ABSTRACT

A piezoelectric element  10  includes a lower electrode, constituted of a Pt/Ti laminated film, a PLT seed layer, formed on the lower electrode, a PZT piezoelectric film, formed on the PLT seed layer, and an upper electrode, formed on the PZT piezoelectric film. A curve Q 1  is a curve drawn such as to pass through a plurality of plotted points, each expressing a PLT (100) peak intensity with respect to a Pt (111) peak intensity according to a substrate setting temperature during forming of the Pt/Ti laminated film. A relationship of the PLT (100) peak intensity with respect to the Pt (111) peak intensity is within a range in the curve Q 1  until the PLT (100) peak intensity decreases by 5% from a peak point P, at which the PLT (100) peak intensity is the maximum, and a (100) orientation rate of PLT constituting the seed layer is not less than 85%.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to a piezoelectric element that includes alower electrode disposed on a substrate, a seed layer formed on thelower electrode, and a piezoelectric film formed on the seed layer.

2. Description of the Related Art

There is known a piezoelectric element that includes a lower electrodedisposed on a substrate, a piezoelectric film formed on the lowerelectrode, and an upper electrode formed on the piezoelectric film. As arepresentative piezoelectric film, there is lead zirconate titanate(PZT: PbZr_(x)Ti_(1-x)O₃). PZT is a perovskite type ferroelectricsubstance and has excellent piezoelectric characteristics. Such apiezoelectric film is formed by a sputtering method, a sol-gel method,etc. Such a piezoelectric element is known to become higher inpiezoelectric characteristics when the PZT is oriented in a (100)direction than in a (111) direction.

SUMMARY OF THE INVENTION

The inventor of preferred embodiments of the present invention describedand claimed in the present application conducted an extensive study andresearch regarding a device using a piezoelectric element and a methodfor manufacturing the same, such as the one described above, and indoing so, discovered and first recognized new unique challenges andpreviously unrecognized possibilities for improvements as described ingreater detail below.

Frequently with a piezoelectric element such as that described above,platinum (Pt), which has stability at high temperature and highconductivity is used as the lower electrode. Pt has a characteristic ofreadily undergoing self-orientation in the (111) direction. Although apiezoelectric film constituted of PZT becomes high in piezoelectriccharacteristics when it is in the (100) orientation, the piezoelectricfilm is influenced by the Pt that is its base and therefore PZT isunlikely to be formed in the (100) orientation on Pt of the (111)orientation. When the piezoelectric film is formed in the (111)orientation, its piezoelectric characteristics degrade.

An object of the present invention is to provide a piezoelectric elementwith high piezoelectric characteristics.

In order to overcome the previously unrecognized and unsolved challengesdescribed above, a preferred embodiment of the present inventionprovides a device using a piezoelectric element. A first piezoelectricelement includes a lower electrode, disposed on a substrate, a seedlayer, formed on the lower electrode and constituted of a sputtered filmhaving PLT as a main component, and a piezoelectric film, formed on theseed layer and having PZT or PLZT as a main component, and the lowerelectrode is constituted of a laminated film of a Ti film at thesubstrate side and a Pt film laminated on the Ti film. Also, when a(111) orientation peak intensity of the Pt constituting the Pt film isrepresented as a Pt (111) peak intensity on an abscissa, a (100)orientation peak intensity of the PLT constituting the seed layer isrepresented as a PLT (100) peak intensity on an ordinate, and a peakcharacteristic curve is a curve joining points of the PLT (100) peakintensity with respect to the Pt (111) peak intensity according tosubstrate setting temperature during forming of the lower electrode, arelationship of the Pt (111) peak intensity and the PLT (100) peakintensity is within a range in the peak characteristic curve until thePLT (100) peak intensity decreases by 5% from a peak point, at which thePLT (100) peak intensity in the peak characteristic curve is themaximum, and a (100) orientation rate of the PLT constituting the seedlayer is not less than 85%.

With the present arrangement, the piezoelectric element, with whichcrystallinity and the (100) orientation of the PLT, constituting theseed layer formed on the Pt film, are satisfactory, is obtained. The(100) orientation of the PZT or the PLZT, constituting the piezoelectricfilm formed on the seed layer, can thereby be made high and thepiezoelectric element having high piezoelectric characteristics isobtained.

A second piezoelectric element includes a lower electrode, disposed on asubstrate, a seed layer, formed on the lower electrode and constitutedof a sputtered film having PLT as a main component, and a piezoelectricfilm, formed on the seed layer and having PZT or PLZT as a maincomponent, and the lower electrode is constituted of a laminated film ofa Ti film at the substrate side and a Pt film laminated on the Ti film.Also, a (111) orientation peak intensity of the Pt constituting the Ptfilm is 17×10000 counts to 35×10000 counts and a (100) orientation rateof the PLT constituting the seed layer is not less than 85%.

With the present arrangement, the (100) orientation of the PLT,constituting the seed layer formed on the Pt film, can be improved. The(100) orientation of the PZT or the PLZT, constituting the piezoelectricfilm formed on the seed layer, can thereby be made high and thepiezoelectric element having high piezoelectric characteristics isobtained.

In the preferred embodiment of the present invention, a film thicknessof the seed layer is 20 nm to 100 nm, a film thickness of the Pt film is50 nm to 200 mm, and a film thickness of the Ti film is not more than 10nm.

In the preferred embodiment of the present invention, the piezoelectricfilm is a piezoelectric film formed by a sol-gel method.

In the preferred embodiment of the present invention, the seed layerhas, near the lower electrode side, a Pb-rich layer high in Pbconcentration.

The preferred embodiment of the present invention further includes anupper electrode formed on the piezoelectric film.

In the preferred embodiment of the present invention, an insulatingfilm, constituted of SiO₂, is interposed between the substrate and thelower electrode.

In the preferred embodiment of the present invention, a lead barrierfilm, constituted of Al₂O₃, is interposed between the insulating filmand the lower electrode.

In the preferred embodiment of the present invention, a film thicknessof the insulating film is 300 nm to 2000 nm.

In the preferred embodiment of the present invention, a film thicknessof the insulating film is 300 nm to 2000 nm and a film thickness of thelead barrier film is 50 nm to 100 nm.

The above and other elements, features, steps, characteristics andadvantages of the present invention will become more apparent from thefollowing detailed description of the preferred embodiments withreference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic sectional view of a piezoelectric elementaccording to a preferred embodiment of the present invention.

FIG. 2 is a flowchart of a manufacturing process of the piezoelectricelement.

FIG. 3 is a graph showing Pt (111) peak intensity, PLT (100) peakintensity, and PLT (100) orientation rate with respect to substratesetting temperature during forming of a Pt/Ti laminated film.

FIG. 4 is a graph showing relationships of the PLT (100) peak intensityand the PLT (100) orientation rate with respect to the Pt (111) peakintensity.

FIG. 5A is an illustrative plan view for describing the arrangement of amain portion of an inkjet printing head in which the piezoelectricelement of FIG. 1 is used.

FIG. 5B is an illustrative plan view of the main portion of the inkjetprinting head of FIG. 5A and is a plan view with a protective substrateomitted.

FIG. 6 is an illustrative sectional view taken along line VI-VI in FIG.5A.

FIG. 7 is an illustrative enlarged sectional view of a portion of asection taken along line VII-VII in FIG. 5A.

FIG. 8 is an illustrative plan view of a pattern example of a lowerelectrode and a piezoelectric film of the inkjet printing head of FIG.5A.

FIG. 9 is an illustrative plan view of a pattern example of aninsulating film of the inkjet printing head of FIG. 5A.

FIG. 10 is an illustrative plan view of a pattern example of apassivation film of the inkjet printing head of FIG. 5A.

FIG. 11 is a bottom view of a main portion of the protective substrateas viewed from an actuator substrate side of the inkjet printing head ofFIG. 5A.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 is a schematic sectional view of a piezoelectric elementaccording to a preferred embodiment of the present invention.

In the present preferred embodiment, the piezoelectric element 10 isformed in contact with a front surface of a lead barrier film 3 formedon a substrate 1. More specifically, an insulating film 2 is formed on afront surface of the substrate 1, and the lead barrier film 3 is formedon a front surface of the insulating film 2.

In the present preferred embodiment, the substrate 1 is constituted of asilicon substrate. A thickness of the silicon substrate 1 isapproximately 100 μm to 1000 μm. The insulating film 2 is constituted ofa silicon oxide film (SiO₂). A film thickness of the insulating film 2is approximately 300 nm to 2000 nm. The lead barrier film 3 isconstituted of alumina (Al₂O₃). A film thickness of the lead barrierfilm 3 is approximately 50 nm to 100 nm.

The piezoelectric element 10 includes a lower electrode 11, formed onthe lead barrier film 3, a seed layer 12, formed on the lower electrode11, a piezoelectric film 13, formed on the seed layer 12, and an upperelectrode 14, formed on the piezoelectric film 13.

The lower electrode 11 is constituted of a laminated film (Pt/Tilaminated film) of a Ti (titanium) film 21, formed on the lead barrierfilm 3, and a Pt (platinum) film 22, formed on the Ti film 21. The Tifilm 21 is formed to improve adhesion of the lead barrier film 3 and thePt film 22. The Pt film 22 has a self-orientation property and isoriented in a (111) direction with respect to the substrate 1. Athickness of the Ti film 21 is approximately several nm to 10 nm, and athickness of the Pt film 22 is approximately 50 nm to 200 nm. In thepresent preferred embodiment, the thickness of the Ti film 21 is 5 nmand the thickness of the Pt film 22 is 200 nm. The thickness of the Tifilm 21 is preferably not more than 10 nm. The Ti film 21 and the Ptfilm 22 are formed by a sputtering method.

The seed layer 12 is a layer provided to improve crystal orientation ofthe piezoelectric film 13 formed on the seed layer 12. In the presentpreferred embodiment, the seed layer 12 is constituted from perovskitetype lead lanthanum titanate (PLT: PbLaTiO₃). PLT is oriented in a (100)direction parallel to a plane (lamination plane) of the substrate 1. Athickness of the seed layer 12 is approximately 20 nm to 100 nm. In thepresent preferred embodiment, the thickness of the seed layer 12 isapproximately 50 nm. The seed layer 12 is formed by the sputteringmethod. A Pb-rich layer, high in Pb concentration, is formed toapproximately 20 nm at a portion inside the seed layer 12 near the lowerelectrode 11 side.

The seed layer 12 may be that with which PLT is doped with Mn(manganese), Mg (magnesium), Nb (niobium), Co (cobalt), Fe (iron), Ni(nickel), Zr (zirconium), Zn (zinc), Al (aluminum), Ta (tantalum), W(tungsten), Ti (titanium), etc. That is, it suffices that the seed layer12 is constituted from a material having PLT as a main component.

In the present preferred embodiment, the piezoelectric film 13 isconstituted from perovskite type lead zirconate titanate (PZT:PbZr_(x)Ti_(1-x)O₃). A thickness of the piezoelectric film 13 isapproximately 1000 nm to 3000 nm. In the present preferred embodiment,the piezoelectric film 13 is formed by a sol-gel method.

The piezoelectric film 13 may be constituted from lead lanthanumzirconate titanate (PLZT), with which a portion of the lead in leadzirconate titanate (PZT) is substituted by lanthanum. Also, thepiezoelectric film 13 may be that with which PZT or PLZT is doped withMn (manganese), Mg (magnesium), Nb (niobium), Co (cobalt), Fe (iron), Ni(nickel), Zr (zirconium), Zn (zinc), Al (aluminum), Ta (tantalum), W(tungsten), Ti (titanium), etc. That is, it suffices that thepiezoelectric film 13 is constituted from a material having PZT as amain component or a material having PLZT as a main component.

In the present preferred embodiment, the upper electrode 14 isconstituted from a laminated film (Ir/IrO₂ laminated film) of an IrO₂(iridium oxide) film 31, formed on the piezoelectric film 13, and an Ir(iridium) film 32, formed on the IrO₂ film 31. A thickness of the upperelectrode 14 is approximately 50 nm to 200 nm. The IrO₂ film 31 and theIr film 32 are formed by the sputtering method. The upper electrode 14may be constituted from a single film of Pt (platinum) instead.

FIG. 2 is a flowchart of a manufacturing process of the piezoelectricelement.

The silicon substrate 1, having the lead barrier film 3 formed on thefront surface via the insulating film 2, is prepared (step S1). Such asilicon substrate 1 is obtained as follows. That is, first, theinsulating film 2, constituted of a thermal oxide film (SiO₂) is formedon the substrate 1 by a thermal oxidation method. Next, the lead barrierfilm 3 is formed on the insulating film 2 by the sputtering method.

Next, the lower electrode 11 is formed on the lead barrier film 3 (stepS2). Specifically, first, the Ti film 21 (of, for example, 5 nm) isformed on the lead barrier film 3 by the sputtering method. Next, the Ptfilm 22 (of, for example, 200 nm) is formed on the Ti film 21 by thesputtering method. A temperature of the substrate 1 during forming ofthe Pt/Ti laminated film by the sputtering method is preferably 515° C.to 575° C. The reason for this shall be explained later. The Ptconstituting the Pt film 22 has the self-orientation property and isthus oriented in the (111) direction with respect to the substrate 1.

Next, the seed layer 12, constituted from PLT, is formed on the lowerelectrode 11 (Pt film 22) by the sputtering method (step S3). In thisprocess, the lower an oxygen partial pressure or lower a sputtering gaspressure, the more a sputtering rate of Pb (lead) increases due to anincrease in energy of Ar ions. The Pb-rich layer that is high in Pbconcentration is thus formed at the portion of the seed layer 12 nearthe lower electrode 11 side.

Next, the piezoelectric film 13, constituted of PZT, is formed on theseed layer 12 by the sol-gel method (step S4).

Lastly, the upper electrode 14 is formed on the piezoelectric film 13(step S5). Specifically, first, the IrO₂ film 31 is formed on thepiezoelectric film 13 by the sputtering method. Next, the Ir film 32 isformed on the IrO₂ film 31 by the sputtering method. The piezoelectricelement 10, constituted of the lower electrode 11, the seed layer 12,the piezoelectric film 13, and the upper electrode 14, is therebyobtained.

During the forming of the Pt film 22 on the Ti film 21 by the sputteringmethod, the Ti in the Ti film 21 diffuses into the Pt film 22. When theTi diffuses to a front surface of the Pt film 22 at an opposite sidefrom the Ti film 21, titanium monoxide (TiO) is formed on the frontsurface of the Pt film 22. It is considered that if TiO is formed on thefront surface of the Pt film 22, then during forming of the seed layer12 on the Ti film 21, the TiO bonds with the Pb of PLT to form PbTiO₃and becomes a nucleus of a PLT crystal and the PLT undergoes crystalgrowth. It is thus considered that if TiO can be formed at a properdensity on the front surface of the Ti film 21, PLT would improve incrystallinity and the (100) orientation of the PLT constituting the seedlayer 12 can be made high.

In the present preferred embodiment, by setting the temperature of thesilicon substrate 1 during the forming of the Pt/Ti laminated film(lower electrode 11) by the sputtering method to an appropriatetemperature, TiO is formed at the proper density on the front surface ofthe Ti film 21 and the (100) orientation of the PLT formed on the Ptfilm 22 is made high. The (100) orientation of the PZT, constituting thepiezoelectric film 13 formed on the seed layer 12, can thereby be madehigh and the piezoelectric element having high piezoelectriccharacteristics is obtained. A proper temperature range of the siliconsubstrate 1, etc., during the forming of the Pt/Ti laminated film (lowerelectrode 11) shall be described later.

FIG. 3 is a graph showing Pt (111) peak intensity, PLT peak intensity,and PLT (100) orientation rate with respect to substrate settingtemperature during the forming of the Pt/Ti laminated film.

The graph of FIG. 3 is prepared as follows. A plurality of samples, eachconstituted of the lower electrode 11 and the seed layer 12, wereprepared with the substrate setting temperature during the forming ofthe lower electrode being changed. Each sample is formed on the leadbarrier film 3 formed, via the insulating film 2, on the siliconsubstrate 1. Then, with each sample, 2θ/θ XRD (X-ray diffraction)measurement was performed to measure the Pt (111) peak intensity[counts], PLT (100) peak intensity [counts], PLT (111) peak intensity[counts], and the PLT (100) orientation rate [%].

The Pt (111) peak intensity is an intensity of a peak that indicates the(111) orientation of the Pt constituting the Pt film 22 inside the lowerelectrode 11.

The PLT (100) peak intensity is an intensity of a peak that indicatesthe (100) orientation of the PLT constituting the seed layer 12.

The PLT (111) peak intensity is an intensity of a peak that indicatesthe (111) orientation of the PLT constituting the seed layer 12.

The PLT (100) orientation rate D is a value expressing the (100)orientation of the PLT constituting the seed layer 12 and is calculatedbased on the following formula:

D={PLT (100) peak intensity/(PLT (100) peak intensity+PLT (111) peakintensity)}×100   (1)

From FIG. 3, it may be considered that a range in which thecrystallinity and the orientation rate of PLT (100) are satisfactory isa range in which the PLT (100) orientation rate D is not less than 85%and the PLT (100) peak intensity is within a range of being decreased by5% from its maximum peak. With the example of a PLT (100) peak intensitycurve of FIG. 3, the peak intensity at a point at which the PLT (100)peak intensity is decreased by 5% from the PLT (100) peak intensity ofthe maximum peak is deemed to be 70×1000 counts.

It is thus preferable to set the substrate setting temperature duringthe forming of the Pt/Ti laminated film to 515° C. to 575° C. In otherwords, with the example of FIG. 3, it is preferable for the Pt (111)peak intensity to be 17×10000 counts to 35×10000 counts, the PLT (100)peak intensity to be not less than 70×1000 counts, and the PLT (100)orientation rate to be not less than 85%.

FIG. 4 is a graph showing relationships of the PLT (100) peak intensityand the PLT (100) orientation rate with respect to the Pt (111) peakintensity.

The graph of FIG. 4 is prepared based on data obtained from a pluralityof samples, such as described with FIG. 3, that differ in the substratesetting temperature during the forming of the Pt/Ti laminated layer. Thedata obtained from each sample are the Pt (111) peak intensity, the PLT(100) peak intensity, the PLT (111) peak intensity, and the PLT (100)orientation rate.

In FIG. 4, a curve Q1 is a curve (peak characteristic curve) drawn suchas to pass through a plurality of plotted points, each expressing thePLT (100) peak intensity with respect to the Pt (111) peak intensityaccording to the substrate setting temperature during the forming of thePt/Ti laminated film (according to sample).

In FIG. 4, a curve Q2 is a curve drawn such as to pass through aplurality of plotted points, each expressing the PLT (100) orientationrate with respect to the Pt (111) peak intensity according to thesubstrate setting temperature during the forming of the Pt/Ti laminatedfilm (according to sample).

The curve Q1 has a peak point (maximum point) P, at which the PLT (100)peak intensity is the maximum, when the Pt (111) peak intensity issubstantially 24×10000 counts. In the curve Q1, an interval of the Pt(111) peak intensity from 80×10000 counts to 24×10000 counts shall bereferred to as a first interval and an interval of the Pt (111) peakintensity of not more than 24×10000 counts shall be referred to as asecond interval.

In the first interval, the PLT (100) peak intensity increases as the Pt(111) peak intensity decreases as indicated by an arrow A. The reasonfor this shall now be explained. The higher the substrate settingtemperature during the formation of the Pt/Ti laminated film, thegreater a diffusion amount of Ti diffusing into the Pt film 22 andtherefore, the lower the Pt (111) peak intensity. Therefore, as the Pt(111) peak intensity decreases from 80×10000 counts, the density of thetitanium monoxide (TiO) formed on the Pt film 22 front surface increasesand the crystallinity of the PLT of the PLT seed layer 12 increases.Therefore, in the first section, the PLT (100) intensity increases asthe Pt (111) peak intensity decreases.

In the second interval, the PLT (100) peak intensity decreases sharplyas the Pt (111) peak intensity decreases as indicated by an arrow B. Thereason for this shall now be explained. The higher the substrate settingtemperature during the formation of the Pt/Ti laminated film, thegreater the diffusion amount of Ti diffusing into the Pt film. However,it is considered that when the amount of Ti diffusing to the Pt film 22front surface exceeds a certain amount, titanium dioxide (TiO₂), whichdoes not become a nucleus of a PLT crystal, is formed on the frontsurface of the Pt film 22 and crystal growth of PLT is inhibited by theTiO₂. Therefore, in the second section, the PLT (100) peak intensitydecreases sharply as the Pt (111) peak intensity decreases. In thefollowing, the point on the curve Q1 at which the PLT (100) peakintensity is the maximum shall be referred to as the peak point P.

From FIG. 4, it may be considered that a range in which thecrystallinity and the orientation rate of PLT (100) are satisfactory isa range in which the PLT (100) orientation rate is high and an influenceof the sharp decrease of the PLT (100) peak intensity due to PLT crystalgrowth inhibition by TiO₂ is small.

From FIG. 4, the range in which the influence of the sharp decrease ofthe PLT (100) peak intensity is small is a range where the relationshipof the PLT (100) peak intensity with respect to the Pt (111) peakintensity is within a range in the curve Q1 until the PLT (100) peakintensity decreases by 5% from the peak point P (within a range of notless than 70×1000 counts in the example of FIG. 4). And within thisrange, a range in which the PLT (100) orientation rate is not less than85% may be considered to be the range in which the crystallinity and theorientation rate of PLT (100) are satisfactory. Therefore, in FIG. 4,the range in which the Pt (111) peak intensity is α to β (the range of17×10000 counts to 35×10000 counts in the example of FIG. 4) is therange in which the crystallinity and the orientation rate of PLT (100)are satisfactory. In other words, the substrate setting temperatureduring the forming of the Pt/Ti laminated film is preferably set suchthat the Pt (111) peak intensity is within the range of α to β in FIG.4.

Although a preferred embodiment of the present invention has beendescribed above, the present invention may also be implemented in yetother preferred embodiments. For example, in the preferred embodimentdescribed above, the lead barrier film 3 is formed on the insulatingfilm 2 and the piezoelectric element 10 is formed such as to contact thefront surface of the lead barrier film 3. However, the lead barrier film3 does not have to be formed on the insulating film 2. That is, thepiezoelectric element 10 is formed such as to contact a front surface ofthe insulating film 2.

Although in the preferred embodiment described above, the piezoelectricfilm 13 is formed by the sol-gel method, it may be formed by thesputtering method instead.

Besides the above, various design changes may be applied within thescope of the matters described in the claims.

Next, an application example of the piezoelectric element 10 of FIG. 1shall be described with reference to FIG. 5A, FIG. 5B, and FIG. 6 toFIG. 11.

FIG. 5A is an illustrative plan view for describing the arrangement of amain portion of an inkjet printing head in which the piezoelectricelement 10 of FIG. 1 is used. FIG. 5B is an illustrative plan view ofthe main portion of the inkjet printing head of FIG. 5A and is a planview with a protective substrate omitted. FIG. 6 is an illustrativesectional view taken along line VI-VI in FIG. 5A. FIG. 7 is anillustrative enlarged sectional view of a portion of a section takenalong line VII-VII in FIG. 5A. FIG. 8 is an illustrative plan view of apattern example of a lower electrode and a piezoelectric film of theinkjet printing head of FIG. 5A.

The arrangement of the inkjet printing head 101 shall now be describedin outline with reference to FIG. 6.

The inkjet printing head 101 includes an actuator substrate 102, anozzle substrate 103, and a protective substrate 104. A movable filmformation layer 110 is laminated on a front surface of the actuatorsubstrate 102. The actuator substrate 102 is equivalent to the substrate1 of FIG. 1 and the movable film formation layer 110 is equivalent tothe insulating film 2 of FIG. 1.

In the actuator substrate 102, ink flow passages (ink reservoirs) 105are formed. In the present application example, the ink flow passages105 are formed to penetrate through the actuator substrate 102. Each inkflow passage 105 is formed to be elongate along an ink flow direction141, which is indicated by an arrow in FIG. 6. Each ink flow passage 105is constituted of an ink inflow portion 106 at an upstream side endportion (left end portion in FIG. 6) in the ink flow direction 141 and apressure chamber 107 (cavity) in communication with the ink inflowportion 106. In FIG. 6, a boundary between the ink inflow portion 106and the pressure chamber 107 is indicated by an alternate long and twoshort dashed line.

The nozzle substrate 103 is constituted, for example, of a siliconsubstrate. The nozzle substrate 103 is adhered to a rear surface 102 bof the actuator substrate 102. The nozzle substrate 103, together withthe actuator substrate 102 and the movable film formation layer 110,defines the ink flow passages 105. More specifically, the nozzlesubstrate 103 defines bottom surface portions of the ink flow passages105. The nozzle substrate 103 has recess portions 103 a each facing apressure chamber 107 and an ink discharge passage 103 b is formed in abottom surface of each recess portion 103 a. Each ink discharge passage103 b penetrates through the nozzle substrate 103 and has a dischargeport 103 c at an opposite side from the pressure chamber 107. Therefore,when a volume change occurs in a pressure chamber 107, the ink retainedin the pressure chamber 107 passes through the ink discharge passage 103b and is discharged from the discharge port 103 c.

Each portion of the movable film formation layer 110 that is a top roofportion of a pressure chamber 107 constitutes a movable film 110A. Themovable film 110A (movable film formation layer 110) is constituted, forexample, of a silicon oxide (SiO₂) film formed on the actuator substrate102. The movable film 110A (movable film formation layer 110) may beconstituted of a laminated film, for example, of a silicon (Si) filmformed on the actuator substrate 102, a silicon oxide (SiO₂) film formedon the silicon film, and a silicon nitride (SiN) film formed on thesilicon oxide film.

In the present specification, the movable film 110A refers to a top roofportion of the movable film formation layer 110 that defines the topsurface portion of the pressure chamber 107. Therefore, portions of themovable film formation layer 110 besides the top roof portions of thepressure chambers 107 do not constitute the movable film 110A.

Each movable film 110A has a thickness of, for example, 0.4 μm to 2 μm.If the movable film 110A is constituted of a silicon oxide film, thethickness of the silicon oxide film may be approximately 1.2 μm. If themovable film 110A is constituted of a laminated film of a silicon film,a silicon oxide film, and a silicon nitride film, the thickness of eachof the silicon film, the silicon oxide film, and the silicon nitridefilm may be approximately 0.4 μm.

Each pressure chamber 107 is defined by a movable film 110A, theactuator substrate 102, and the nozzle substrate 103 and is formed to asubstantially rectangular parallelepiped shape in the presentapplication example. The pressure chamber 107 may, for example, have alength of approximately 800 μm and a width of approximately 55 μm. Eachink inflow portion 106 is in communication with one end portion in along direction of a pressure chamber 107.

A piezoelectric element 10 is disposed on a front surface of eachmovable film 110A. Each piezoelectric element 10 includes a lowerelectrode 11 formed on the movable film formation layer 110, a seedlayer (not shown) formed on the lower electrode 11, a piezoelectric film13 formed on the seed layer, and an upper electrode 14 formed on thepiezoelectric film 13.

Although the seed layer formed on the lower electrode 11 is equivalentto the seed layer 12 of FIG. 1, illustration thereof is omitted in theapplication example. Although in the present application example, abarrier film, equivalent to the lead barrier film 3 of FIG. 1, is notformed on the front surface of the movable film 110A, a barrier film,equivalent to the lead barrier film 3 of FIG. 1, may be formed.

The upper electrode 14 is constituted of a laminated film (Ir/IrO₂laminated film) of an IrO₂ (iridium oxide) film formed on thepiezoelectric film 13 and an Ir (iridium) film formed on the IrO₂ film31. The upper electrode 14 may have a thickness, for example, ofapproximately 0.2 μm.

As the piezoelectric film 13, for example, a PZT (PbZr_(x)Ti_(1-x)O₃:lead zirconate titanate) film formed by a sol-gel method or a sputteringmethod is used. Such a piezoelectric film 13 is constituted of asintered body of a metal oxide crystal. The piezoelectric film 13includes active portions 13A, each in contact with a lower surface of anupper electrode 14, and an inactive portion 13B extending along a frontsurface of the movable film formation layer 110 from entire peripheriesof side portions of the active portions 13A. The active portions 13A areformed to be of the same shape as the upper electrodes 14 in plan view.

Each active portion 13A has a thickness of approximately 1 μm. Theinactive portion 13B has a thickness thinner than the thickness of theactive portion 13A. The thickness of the inactive portion 13B ispreferably not less than 1/20 and not more than 1/10 the thickness ofthe active portion 13A. The overall thickness of each movable film 110Ais preferably approximately the same as the thickness of the activeportion 13A or approximately ⅔ the thickness of the active portion 13A.

The seed layer (not shown) formed on the lower electrode 11 is a layerprovided to improve the crystal orientation of the piezoelectric film 13formed on the seed layer. The seed layer is formed to the same shape asthe piezoelectric film 13 in plan view. In the present preferredembodiment, the seed layer is constituted from perovskite type leadlanthanum titanate (PLT: PbLaTiO₃).

The lower electrode 11 is constituted of a laminated film (Pt/Tilaminated film) of a Ti (titanium) film 21 formed on the movable filmformation layer 110 and a Pt (platinum) film 22 formed on the Ti film21. The lower electrode 11 has main electrode portions 11A, facing lowersurfaces of the active portions 13A of the piezoelectric film 13, and anextension portion 11B extending along the front surface of the movablefilm formation layer 110 from entire peripheries of the main electrodeportions 11A. The lower electrode 11 may have a thickness, for example,of approximately 0.2 μm.

A hydrogen barrier film 114 is formed on the inactive portion 13B of thepiezoelectric film 13 and on the piezoelectric element 10. The hydrogenbarrier film 114 is constituted, for example, of Al₂O₃ (alumina). Thehydrogen barrier film 114 has a thickness of approximately 50 nm to 100nm. The hydrogen barrier film 114 is provided to prevent degradation ofcharacteristics of the piezoelectric film 13 due to hydrogen reduction.

An insulating film 115 is laminated on the hydrogen barrier film 114.The insulating film 115 is constituted, for example, of SiO₂ orlow-hydrogen SiN, etc. The insulating film 115 has a thickness ofapproximately 500 nm. Upper wirings 117, a lower wiring 118, and dummywirings 119 are formed on the insulating film 115. These wirings 117,118, and 119 may be constituted of a metal material that includes Al(aluminum). These wirings 117, 118, and 119 have a thickness, forexample, of approximately 1000 nm (1 μm).

One end portion of each upper wiring 117 is disposed above one endportion (downstream side end portion in the ink flow direction 141) ofan upper electrode 14. A contact hole 133, penetrating continuouslythrough the hydrogen barrier film 114 and the insulating film 115, isformed between the upper wiring 117 and the upper electrode 14. The oneend portion of the upper wiring 117 enters into the contact hole 133 andis connected to the upper electrode 14 inside the contact hole 133. Fromabove the upper electrode 14, the upper wiring 117 crosses an outer edgeof the pressure chamber 107 and extends outside the pressure chamber107.

The lower wiring 118 is disposed above the extension portion 11B of thelower electrode 11 at an opposite side from the pressure chamber 107with respect to the ink inflow portion 106 of the ink flow passage 105.A plurality of contact holes 134, penetrating continuously through theseed layer (not shown), the inactive portion 13B of the piezoelectricfilm 13, the hydrogen barrier film 114, and the insulating film 115, areformed between the lower wiring 118 and the extension portion 11B of thelower electrode 11. The lower wiring 118 enters into the contact holes134 and is connected to the extension portion 11B of the lower electrode11 inside the contact holes 134.

The dummy wirings 119 are not electrically connected to either of theupper wirings 117 and the lower wiring 118 and are electricallyinsulated wirings. The dummy wirings 119 are formed in the same step asa step in which the upper wirings 117 and the lower wiring 118 areformed.

A passivation film 121, covering the wirings 117, 118, and 119 and theinsulating film 115 is formed on the insulating film 115. Thepassivation film 121 is constituted, for example, of SiN (siliconnitride). The passivation film 121 may have a thickness, for example, ofapproximately 800 nm.

Pad openings 135 that expose portions of the upper wirings 117 areformed in the passivation film 121. The pad openings 135 are formed in aregion outside the pressure chambers 107 and are formed, for example, attip portions (end portions at opposite sides from the portions ofcontact with the upper electrodes 14) of the upper wirings 117. Pads 142that cover the pad openings 135 are formed on the passivation film 121.The pads 142 enter into the pad openings 135 and are connected to theupper wirings 117 inside the pad openings 135.

Ink supply penetrating holes 122, penetrating through the passivationfilm 121, the insulating film 115, the hydrogen barrier film 114, theinactive portion 13B, the seed layer (not shown), the lower electrode11, and the movable film formation layer 110 are formed at positionscorresponding to end portions of the ink flow passages 105 at the inkinflow portion 106 sides. Penetrating holes 123, each including an inksupply penetrating hole 122 and being larger than the ink supplypenetrating hole 122, are formed in the inactive portion 13B, the seedlayer, and the lower electrode 11. The hydrogen barrier film 114 entersinto gaps between the penetrating holes 123, in the inactive portion13B, the seed layer, and the lower electrode 11, and the ink supplypenetrating holes 122. The ink supply penetrating holes 122 are incommunication with the ink inflow portions 106.

The protective substrate 104 is constituted, for example, of a siliconsubstrate. The protective substrate 104 is disposed above the actuatorsubstrate 102 such as to cover the piezoelectric elements 10. Theprotective substrate 104 is bonded to the passivation film 121 via anadhesive 150. The protective substrate 104 has housing recesses 152 in afacing surface 151 that faces a front surface 102 a of the actuatorsubstrate 102. The piezoelectric elements 10 are housed inside thehousing recesses 152. Further, the protective substrate 104 has formedtherein ink supply passages 153 that are in communication with the inksupply penetrating holes 122. The ink supply passages 153 penetratethrough the protective substrate 104. An ink tank (not shown) storingink is disposed on the protective substrate 104.

Each piezoelectric element 10 is formed at a position facing a pressurechamber 107 across a movable film 110A. That is, the piezoelectricelement 10 is formed to contact a front surface of the movable film 110Aat the opposite side from the pressure chamber 107. Each pressurechamber 107 is filled with ink by the ink being supplied from the inktank to the pressure chamber 107 through an ink supply passage 153, anink supply penetrating hole 122, and an ink inflow portion 106. Themovable film 110A defines a top surface portion of the pressure chamber107 and faces the pressure chamber 107. The movable film 110A issupported by portions of the actuator substrate 102 at a periphery ofthe pressure chamber 107 and has flexibility enabling deformation in adirection facing the pressure chamber 107 (in other words, in thethickness direction of the movable film 110A).

The upper wirings 117 and the lower wiring 118 are connected to a drivecircuit (not shown). Specifically, the pads 142 of the upper wirings 117and the drive circuit are connected via a connecting metal member (notshown). As shall be described later, a pad 143 (see FIG. 5A) isconnected to the lower wiring 118. The pad 143 of the lower wiring 118and the drive circuit are connected via a connecting metal member (notshown). When a drive voltage is applied from the drive circuit to apiezoelectric element 10, the active portion 13A of the piezoelectricfilm 13 deforms due to an inverse piezoelectric effect. The movable film110A is thereby made to deform together with the piezoelectric element10 to bring about a volume change of the pressure chamber 107 and theink inside the pressure chamber 107 is pressurized. The pressurized inkpasses through the ink discharge passage 103 b and is discharged asmicrodroplets from the discharge port 103 c.

The arrangement of the inkjet printing head 101 shall now be describedin more detail with reference to FIG. 5A to FIG. 8.

A plurality of the ink flow passages 105 (pressure chambers 107) areformed as stripes extending parallel to each other in the actuatorsubstrate 102. The piezoelectric element 10 is disposed respectively ineach of the plurality of ink flow passages 105. The ink supplypenetrating holes 122 are provided respectively for each of theplurality of ink flow passages 105. The housing recesses 152 and the inksupply passages 153 in the protective substrate 104 are providedrespectively for each of the plurality of ink flow passages 105.

The plurality of ink flow passages 105 are formed at equal intervalsthat are minute intervals (for example, of approximately 30 μm to 350μm) in a width direction thereof. Each ink flow passage 105 is elongatealong the ink flow direction 141. Each ink flow passage 105 isconstituted of an ink inflow portion 106 in communication with an inksupply penetrating hole 122 and the pressure chamber 107 incommunication with the ink inflow portion 106.

In plan view, the pressure chamber 107 has an oblong shape that iselongate along the ink flow direction 141. That is, the top surfaceportion of the pressure chamber 107 has two side edges along the inkflow direction 141 and two end edges along a direction orthogonal to theink flow direction 141.

In plan view, the ink inflow portion 106 has substantially the samewidth as the pressure chamber 107. An inner surface of an end portion ofthe ink inflow portion 106 at an opposite side from the pressure chamber107 is formed to a semicircle in plan view. The ink supply penetratinghole 122 is circular in plan view (see especially FIG. 5B).

Each piezoelectric element 10 has, in plan view, a rectangular shapethat is long in a long direction of a pressure chamber 107 (movable film110A). A length in a long direction of the piezoelectric element 10 isshorter than a length in the long direction of the pressure chamber 107(movable film 110A). As shown in FIG. 5B, respective end edges along ashort direction of the piezoelectric element 10 are disposed at innersides at predetermined intervals respectively from respectivecorresponding end edges of the movable film 110A. Also, a width in theshort direction of the piezoelectric element 10 is narrower than a widthin a short direction of the movable film 110A. Respective side edgesalong the long direction of the piezoelectric element 10 are disposed atinner sides at predetermined intervals from respective correspondingside edges of the movable film 110A.

The lower electrode 11 is formed on substantially an entirety of thefront surface of the movable film formation layer 110 (see especiallyFIG. 8). The lower electrode 11 is a common electrode used in common forthe plurality of piezoelectric elements 10. The lower electrode 11includes the main electrode portions 11A of rectangular shape in planview that constitute the piezoelectric elements 10 and the extensionportion 11B led out from the main electrode portions 11A in directionsalong the front surface of the movable film formation layer 110 toextend outside the peripheral edges of the top surface portions of thepressure chambers 107.

A length in a long direction of each main electrode portion 11A isshorter than the length in the long direction of each movable film 110A.Respective end edges of the main electrode portion 11A are disposed atinner sides at predetermined intervals respectively from the respectivecorresponding end edges of the movable film 110A. Also, a width in ashort direction of the main electrode portion 11A is narrower than thewidth of the movable film 110A in the short direction. Respective sideedges of the main electrode portion 11A are disposed at inner sides atpredetermined intervals from the respective corresponding side edges ofthe movable film 110A. The extension portion 11B is a region of theentire region of the lower electrode 11 excluding the main electrodeportions 11A.

In plan view, the upper electrodes 14 are formed to rectangular shapesof the same pattern as the main electrode portions 11A of the lowerelectrode 11. That is, a length in a long direction of each upperelectrode 14 is shorter than the length in the long direction of eachmovable film 110A. Respective end edges of the upper electrode 14 aredisposed at inner sides at predetermined intervals respectively from therespective corresponding end edges of the movable film 110A. Also, awidth in a short direction of the upper electrode 14 is narrower thanthe width in the short direction of the movable film 110A. Respectiveside edges of the upper electrode 14 are disposed at inner sides atpredetermined intervals from the respective corresponding side edges ofthe movable film 110A.

In plan view, the piezoelectric film 13 is formed to be of the samepattern as the lower electrode 11 (see FIG. 9). That is, thepiezoelectric film 13 is formed across substantially an entirety of thefront surface of the movable film formation layer 110. As mentionedabove, the piezoelectric film 13 includes the active portions 13A andthe inactive portion 13B. In plan view, the active portions 13A areformed to rectangular shapes of the same pattern as the upper electrodes14. That is, a length in a long direction of each active portion 13A isshorter than the length in the long direction of each movable film 110A.Respective end edges of the active portion 13A are disposed at innersides at predetermined intervals respectively from the respectivecorresponding end edges of the movable film 110A. Also, a width in ashort direction of the active portion 13A is narrower than the width inthe short direction of the movable film 110A. Respective side edges ofthe active portion 13A are disposed at inner sides at predeterminedintervals from the respective corresponding side edges of the movablefilm 110A. A lower surface of the active portion 13A contacts an uppersurface of the main electrode portion 11A of the lower electrode 11 andan upper surface of the active portion 13A contacts a lower surface ofthe upper electrode 14.

In plan view, the inactive portion 13B is formed to be of the samepattern as the extension portion 11B of the lower electrode 11. Theinactive portion 13B extends from entire peripheries of side walls ofthe active portions 13A to an outer side beyond the peripheral edges ofthe pressure chambers 107. An upper surface of the inactive portion 13Bis covered by the hydrogen barrier film 114.

The seed layer formed on the lower electrode 11 is formed to be of thesame pattern as the piezoelectric film 13 in plan view.

In the present application example, the piezoelectric film 13 includesthe inactive portion 13B that is led out from the entire peripheries ofthe side portions of the active portions 13A in directions along thefront surface of the movable film formation layer 110 and is thinner inthickness than the active portions 13A. Therefore, a path putting anupper electrode 14 and the lower electrode 11 in communication along anouter surface of the piezoelectric film 13 is made longer in length thanin a case where the piezoelectric film 13 does not include the inactiveportion 13B. Therefore, even if a metal thin film is formed on an outersurface of the piezoelectric film 13 in patterning the piezoelectricfilm 13 by etching, a leak path will be long and increase of leakcurrent can thus be suppressed. Increase of leak current can also besuppressed because in patterning the piezoelectric film 13 by etching, ametal thin film is less likely to form on the upper surface of theinactive portion 13B than on side surfaces of the active portions 13A oron a side surface of the inactive portion 13B.

An annular region in each movable film 110A between peripheral edges ofthe movable film 110A and peripheral edges of the piezoelectric element10 is a region that is not constrained by the piezoelectric element 10or a peripheral wall of the pressure chamber 107 and is a region inwhich a large deformation occurs. That is, a peripheral edge portion ofthe movable film 110A is a region in which a large deformation occurs.

Therefore, when the piezoelectric element 10 is driven, the peripheraledge portion of the movable film 110A bends such that an innerperipheral edge side of the peripheral edge portion of the movable film110A is displaced in a thickness direction of the pressure chamber 107(downward in the present application example) and an entirety of acentral portion surrounded by the peripheral edge portion of the movablefilm 110A is thereby displaced in the thickness direction of thepressure chamber 107 (downward in the present application example).Thus, cracking occurs readily in the peripheral edge portion of themovable film 110A because it is such a region in which a largedeformation occurs.

In the present application example, the inactive portion 13B, in planview, extends outward across the peripheral edges of the movable film110A from the entire peripheries of the side surfaces of the activeportions 13A. That is, the inactive portion 13B of the piezoelectricfilm 13 is interposed above the peripheral edge portions of the movablefilms 110A. Cracking of the peripheral edge portions of the movable film110A can thus be suppressed.

Each upper wiring 117 extends from an upper surface of one end portionof a piezoelectric element 10 and along an end surface of thepiezoelectric element 10 continuous to the upper surface and extendsfurther along the front surface of the inactive portion 13B of thepiezoelectric film 13 in a direction along the ink flow direction 141.The tip portion of the upper wiring 117 is disposed further downstreamin the ink flow direction 141 than a downstream side end of theprotective substrate 104.

The pad openings 135 that expose central portions of tip portion frontsurfaces of the upper wirings 117 are formed in the passivation film121. The pads 142 are provided on the passivation film 121 such as tocover the pad openings 135. The pads 142 are connected to the upperwirings 117 inside the pad openings 135.

In plan view, the lower wiring 118 has a rectangular main wiring portion118A that is long in a direction orthogonal to the ink flow direction141 and a lead portion 118B extending along the ink flow direction 141from one end portion of the main wiring portion 118A. A tip portion ofthe lead portion 118B is disposed further downstream in the ink flowdirection 141 than the downstream side end of the protective substrate104.

The lower wiring 118 enters into the plurality of contact holes 134 andis connected to the extension portion 11B of the lower electrode 11inside the contact holes 134. A pad opening 136 that exposes a centralportion of a tip portion front surface of the lead portion 118B isformed in the passivation film 121. The pad 143 is provided on thepassivation film 121 such as to cover the pad opening 136. The pad 143is connected to the lead portion 118B inside the pad opening 136.

FIG. 11 is a bottom view of a main portion of the protective substrateas viewed from the actuator substrate side of the inkjet printing head.

As shown in FIG. 5A, FIG. 7, and FIG. 11, in the facing surface 151 ofthe protective substrate 104, the plurality of housing recesses 152 areformed in parallel at intervals in a direction orthogonal to the inkflow direction 141. In plan view, the plurality of housing recesses 152are disposed at positions facing the plurality of pressure chambers 107.With respect to the respective housing recesses 152, the ink supplypassages 153 are disposed at upstream sides in the ink flow direction141. In plan view, each housing recess 152 is formed to a rectangularshape slightly larger than the pattern of the upper electrode 14 of thecorresponding piezoelectric element 10. The corresponding piezoelectricelement 10 is housed in each housing recess 152.

In plan view, the ink supply passages 153 of the protective substrate104 have circular shapes of the same pattern as the ink supplypenetrating holes 122 at the actuator substrate 102 side. In plan view,the ink supply passages 153 are matched with the ink supply penetratingholes 122.

In plan view, the dummy wirings 119 include first dummy wirings 119A ofcircular annular shapes that surround the ink supply passages 153 (inksupply penetrating holes 122). Above the actuator substrate 102, thefirst dummy wirings 119A are disposed in regions facing regions of thefacing surface 151 of the protective substrate 104 peripheral to the inksupply passages 153. A width of each first dummy wiring 119A (differencebetween an inner diameter and an outer diameter of each first dummywiring 119A) is preferably not less than ⅓ a diameter of each ink supplypassage 153. Upper surfaces of the first dummy wirings 119A are flat.Each first dummy wiring 119A constitutes a base 120 that supports theprotective substrate 104 and increases adhesion with the facing surfaceof the protective substrate 104.

The dummy wirings 119 further include second dummy wirings 119B ofelongate rectangular shapes that are formed at width central portions ofregions between adjacent pressure chambers 107 and at outward sides ofthe pressure chambers 107 at respective outer sides of the set ofplurality of pressure chambers and extend in the direction along the inkflow direction 141. Upper surfaces of the second dummy wirings 119B areflat. Each second dummy wiring 119B constitutes a base that supports theprotective substrate 104 and increases adhesion with the facing surfaceof the protective substrate 104.

In bonding the protective substrate 104 to the actuator substrate 102,the protective substrate 104 is pressed against the actuator substrate102 in a state where the adhesive 150 is coated on a portion of bondingof the actuator substrate 102 and the protective substrate 104. In thisprocess, the facing surface 151 of the protective substrate 104 ispressed via the passivation film 121 against the first dummy wirings119A and the second dummy wirings 119B that are the bases with flatupper surfaces.

The facing surface 151 of the protective substrate 104 is thus bondedfirmly via the passivation film 121 and the adhesive 150 to the uppersurfaces of the first dummy wirings 119A and the second dummy wirings119B. Defective adhesion is thus made unlikely to occur at the portionof bonding of the facing surface 151 of the protective substrate 104 andthe actuator substrate 102.

In the present application example, by the first dummy wirings 119A(bases 120) of circular annular shapes surrounding the ink supplypassages 153 (ink supply penetrating holes 122) being provided at theactuator substrate 102 side, occurrence of defective bonding betweenlower surfaces of wall portions of the protective substrate 104 betweenthe housing recesses 152 and the ink supply passages 153 and theactuator substrate 102 can be suppressed. Leakage of ink into a housingrecess 152 from an ink supply passage 153 can thereby be suppressed.

FIG. 9 is an illustrative plan view of a pattern example of theinsulating film of the inkjet printing head. FIG. 10 is an illustrativeplan view of a pattern example of the passivation film of the inkjetprinting head.

In the present application example, above the actuator substrate 102,the insulating film 115 and the passivation film 121 are formed onsubstantially an entirety of a region of the protective substrate 104outside the housing recesses 152 in plan view. However, in this region,the ink supply penetrating holes 122 and the contact holes 134 areformed in the insulating film 115. In this region, the ink supplypenetrating holes 122 and the pad openings 135 and 136 are formed in thepassivation film 121.

In the regions of the protective substrate 104 inside the housingrecesses 152, the insulating film 115 and the passivation film 121 areformed just in one end portions (upper wiring regions) in which theupper wirings 117 are present. In each of these regions, the passivationfilm 121 is formed to cover an upper surface and a side surface of anupper wiring 117 on the insulating film 115. In other words, in theinsulating film 115 and the passivation film 121, openings 137 areformed in regions, within the inner side regions of the housing recesses152 in plan view, that exclude the upper wiring regions. The contactholes 133 are further formed in the insulating film 115.

In the present application example, in a region at the inner side of theperipheral edge of each pressure chamber 107 in plan view, theinsulating film 115 and the passivation film 121 are formed just in theupper wiring region in which an upper wiring 117 is present. Therefore,most of the side surface and the upper surface of each piezoelectricelement are not covered by the insulating film 115 and the passivationfilm 121. Displacement of each movable film 110A can thereby beincreased in comparison to a case where entireties of the side surfaceand the upper surface of the piezoelectric element 10 are covered by theinsulating film and the passivation film.

The present application corresponds to Japanese Patent Application No.2017-171445 filed in the Japan Patent Office on Sep. 6, 2017 andJapanese Patent Application No. 2018-152009 filed in the Japan PatentOffice on Aug. 10, 2018, and the entire disclosures of theseapplications are incorporated herein by reference.

While preferred embodiments of the present invention have been describedabove, it is to be understood that variations and modifications will beapparent to those skilled in the art without departing the scope andsprit of the present invention. The scope of the present invention,therefore, is to be determined solely by the following claims.

What is claimed is:
 1. A piezoelectric element, comprising: a lowerelectrode, disposed on a substrate; a seed layer, formed on the lowerelectrode and constituted of a sputtered film having PLT as a maincomponent; and a piezoelectric film, formed on the seed layer and havingPZT or PLZT as a main component; and wherein the lower electrode isconstituted of a laminated film of a Ti film at the substrate side and aPt film laminated on the Ti film, the piezoelectric element being suchthat when a (111) orientation peak intensity of the Pt constituting thePt film is represented as a Pt (111) peak intensity on an abscissa, a(100) orientation peak intensity of the PLT constituting the seed layeris represented as a PLT (100) peak intensity on an ordinate, and a peakcharacteristic curve is a curve joining points of the PLT (100) peakintensity with respect to the Pt (111) peak intensity according tosubstrate setting temperature during forming of the lower electrode, arelationship of the Pt (111) peak intensity and the PLT (100) peakintensity is within a range in the peak characteristic curve until thePLT (100) peak intensity decreases by 5% from a peak point, at which thePLT (100) peak intensity is the maximum, and a (100) orientation rate ofthe PLT constituting the seed layer is not less than 85%.
 2. Thepiezoelectric element according to claim 1, wherein a film thickness ofthe seed layer is 20 nm to 100 nm, a film thickness of the Pt film is 50nm to 200 mm, and a film thickness of the Ti film is not more than 10nm.
 3. The piezoelectric element according to claim 1, wherein thepiezoelectric film is a piezoelectric film formed by a sol-gel method.4. The piezoelectric element according to claim 1, wherein the seedlayer has, near the lower electrode side, a Pb-rich layer high in Pbconcentration.
 5. The piezoelectric element according to claim 1,further comprising: an upper electrode formed on the piezoelectric film.6. The piezoelectric element according to claim 1, wherein an insulatingfilm, constituted of SiO₂, is interposed between the substrate and thelower electrode.
 7. The piezoelectric element according to claim 6,wherein a lead barrier film, constituted of Al₂O₃, is interposed betweenthe insulating film and the lower electrode.
 8. The piezoelectricelement according to claim 6, wherein a film thickness of the insulatingfilm is 300 nm to 2000 nm.
 9. The piezoelectric element according toclaim 7, wherein a film thickness of the insulating film is 300 nm to2000 nm and a film thickness of the lead barrier film is 50 nm to 100nm.
 10. A piezoelectric element comprising: a lower electrode, disposedon a substrate; a seed layer, formed on the lower electrode andconstituted of a sputtered film having PLT as a main component; and apiezoelectric film, formed on the seed layer and having PZT or PLZT as amain component; and wherein the lower electrode is constituted of alaminated film of a Ti film at the substrate side and a Pt filmlaminated on the Ti film, the piezoelectric element being such that a(111) orientation peak intensity of the Pt constituting the Pt film is17×10000 counts to 35×10000 counts and a (100) orientation peakintensity of the PLT constituting the seed layer is not less than70×1000 counts.
 11. The piezoelectric element according to claim 10,wherein a film thickness of the seed layer is 20 nm to 100 nm, a filmthickness of the Pt film is 50 nm to 200 mm, and a film thickness of theTi film is not more than 10 nm.
 12. The piezoelectric element accordingto claim 10, wherein the piezoelectric film is a piezoelectric filmformed by a sol-gel method.
 13. The piezoelectric element according toclaim 10, wherein the seed layer has, near the lower electrode side, aPb-rich layer high in Pb concentration.
 14. The piezoelectric elementaccording to claim 10, further comprising: an upper electrode formed onthe piezoelectric film.
 15. The piezoelectric element according to claim10, wherein an insulating film, constituted of SiO₂, is interposedbetween the substrate and the lower electrode.
 16. The piezoelectricelement according to claim 15, wherein a lead barrier film, constitutedof Al₂O₃, is interposed between the insulating film and the lowerelectrode.
 17. The piezoelectric element according to claim 15, whereina film thickness of the insulating film is 300 nm to 2000 nm.
 18. Thepiezoelectric element according to claim 16, wherein a film thickness ofthe insulating film is 300 nm to 2000 nm and a film thickness of thelead barrier film is 50 nm to 100 nm.